Dysarthria is a form of motor speech disorder, which occurs when the muscles that control speech become weak or uncoordinated.[1] Dysarthria is not a disease itself; it results from several diseases and conditions such as cerebral palsy,[2][3] muscular dystrophy,[4][5] amyotrophic lateral sclerosis (ALS), Parkinson’s disease,[6] multiple sclerosis,[7] Guillain-Barré syndrome, and other neuromuscular diseases.[8] Dysarthria is characterized by indistinct articulation because of decreased muscular control.
Since not all people with dysarthria have the same types of weakness, treatment will vary from person to person across a wide range of options. Treatment options will be determined by a speech-language pathologist (SLP) after careful examination of the individual’s underlying cause of their weakness or problems with coordination. The SLP may also refer the patient to an otolaryngologist for further evaluation if they suspect that there is a neurological disorder affecting muscle movement in addition to having a motor speech disorder.
Dysarthria is caused by problems with the muscles used for speaking. Dysarthria develops when lesions or degeneration affects part of the nervous system where motor control signals are sent (motor cortex, upper motor neuron lesion). Dysarthria can also develop due to damage to nerves that connect to muscles of speech production (lower motor neuron lesion)[9]. Dysarthria may occur in diseases such as Parkinson’s disease,[10] ALS, multiple sclerosis,[11] and Alzheimer’s disease.[12]
It may also result from trauma, stroke, tumors on the brain stem, infections such as meningitis, encephalitis or poliomyelitis,[13][14][15] viral illness,[16][17][18][19] overuse injuries, otitis media,[20][21] and other head or neck injuries. Dysarthria can also be caused by brain tumors, which can cause compression of critical structures in the brain.[22]
Dysarthria may affect vocal loudness, inflection or tone of voice, pitch control, articulation (lack of facial movement), resonance (formation of vowels and consonants), fluency (the ability to begin and continue speech smoothly), accuracy (proper placement of sounds when speaking).[23] Dysarthria may result in slurred or nasal speech because airflow is impeded or because proper formation of syllables is impaired.
Dysarthria is classified as a major subtype of dysphasia, which also includes the types of Dysphagia & Dyslalia. Dysarthria can be caused by impairment to one or more regions that are involved in speech generation including motor coordination, orofacial muscle control, respiratory control, and vocal fold function. Dysarthria occurs mainly due to an impaired neuromuscular system within the muscles responsible for controlling speech.
It has been found that 65% of people who have this disorder usually have other medical problems associated with it such as Parkinson’s disease, Multiple Sclerosis (MS), amyotrophic lateral sclerosis (ALS), strokes, brain tumors, traumatic brain injury (TBI) and cerebral palsy (CP). Dysarthria can also occur in the absence of any other disorder and is then called Primary Dysarthria. Dysarthria can be divided into three main classifications: Flaccid Dysarthria, Hyperkinetic Dysarthria, Mixed Dysarthrias.
This man presents with a mild-moderate dysarthria with an intelligibility rate of 70%. The primary characteristics of his dysarthria are slow rate, nasal resonance, imprecise consonants, breathy voice quality, inappropriate silence, reduced stress and excessive tension. Dysarthrias include several speech disorders that cause someone to have difficulty speaking because of abnormal muscle control or coordination problems. Dysrhythmic or irregular rhythm is another sign that distinguishes dysarthria from other speech disorders.
Dysarthrias are often present among people who have had a cerebrovascular accident, brain tumor or stroke. Dysarthria can be caused by any disease that disturbs the coordination of muscle tone and movement during speech production including amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), cerebral palsy, muscular dystrophy and Parkinson’s disease (PD). Dysarthria usually occurs on both sides; however, it is possible for dysarthria to affect one side of the body exclusively or in combination with some disorder affecting vocal fold function like spasmodic Dysphonia.
Dysarthrias include: Spastic Dysarthria- This type of Dysarthria is most common in adults with brain injuries. Dysarthria is usually caused by an upper motor neuron disorder that affects the muscles under voluntary control, resulting in stiff and slow speech. Dysarthria can also be referred to as Spastic Dysphonia or Dysphonic Dysarthria.
Flaccid Dysarthria- This type of Dysarthria involves muscle weakness, which causes the vocal tract to lose its normal stability during speech production. Hyperkinetic Dysarthria- This type of Dysarthria includes involuntary movements related to muscle rigidity or spasms called tics. Although most individuals with tardive dyskinesia have a flaccid type of dyskinesia, some people may experience hyperkinetic dysarthria as well. Dysarthria resulting from a mixed form of Dyskinesia can also be called Dyskinetic Dysarthria. Mixed Dysarthria- This type is often referred to as Dysphonic Dysarthria because it includes some combination of hyperkinetic and spastic or flaccid movement disorders.
For example, in response to a question that she does not understand, the client demonstrates use of the oral musculature that includes a blinking jaw and a protruded lower lip. Dysarthria can be classified as being either neuromuscular, central or peripheral depending on the location of the lesion. A motor speech disorder is any disruption in movement used for producing speech sounds or signs caused by impairment in structures responsible for generating movements necessary for speaking. Dysarthria is an identifiable condition representing one of several possible deficits attributed to impaired control of muscle function.
Dysarthria can refer to slurred, slow, effortful and muted speech produced with incompletely filled pauses due to problems with coordination between respiratory muscles and vocal fold muscles. Dysarthria is also characterized by disruptions in the rhythm, rate, and loudness of speech. Dysarthria has been determined to exist when a person exhibits verbal production that is characterized by slurring or articulatory breakdowns. Dysarthria can be a result of a neurological disorder affecting motor function within the central nervous system (CNS) such as a cerebrovascular accident, traumatic brain injury or multiple sclerosis.
Dysarthria can also arise from damage to peripheral nerves from progressive neuropathies such as amyotrophic lateral sclerosis/motor neuron disease. Dysarthria’s pathophysiology results from damage to parts within the central and peripheral nervous systems which control muscle movements necessary for speaking effectively. In other words, dysarthria occurs when there is a disruption in the neuromuscular coordination necessary for producing speech. Dysarthria is a motor speech disorder that involves muscle tone and strength, which results from damage to parts within the central or peripheral nervous system.
Dysarthria can be either: congenital (present at birth), developmental (appears as a child grows and develops), or acquired (symptomatic of other conditions). The following will focus on acquired dysarthria caused by brain injuries. Dysarthria can affect any part of the process involved in speaking, including auditory processing, language comprehension, memory processes, word formation processes, spoken language formulation processes or verbal expression formulations. Dysarthria is often confused with apraxia of speech because some individuals who have dysarthria also have apraxia of speech.
Dysarthria can result in a limited number of sounds or phonemes because it affects the ability to move the muscles that help produce speech, thus making it difficult to articulate words and sentences. Dysarthria also makes it more challenging for someone with dysarthria to speak clearly because they may misplace sounds, syllables, or entire words while speaking. Dysarthria varies greatly in severity; some individuals experience mild disruptions in movement while others struggle with extremely labored speech production process. Dysarthria is prevalent among people who have stroke (CVA).
